The present invention relates, in general, to subterranean fluids, and more particularly, to subterranean drilling fluids that may be useful for reducing the production of water from a portion of a subterranean formation and/or stabilizing an unconsolidated portion of a subterranean formation while drilling.
The production of water with hydrocarbons from subterranean wells generally is problematic and expensive. While hydrocarbon-producing wells are usually completed in hydrocarbon-bearing formations, such formations may contain, or may be adjacent to, water-bearing sections. Generally, the term “water-bearing section” refers to any portion of a subterranean formation that may produce water, including a hydrocarbon-bearing section that has sufficiently high water content such that water may be produced along with hydrocarbons. Water is highly mobile and easily may flow into the well bore by way of natural fractures and/or high permeability streaks that may be present in the formation. Over the life of such wells, the ratio of water to hydrocarbons recovered may be undesirable in view of the cost of producing the water, separating it from the hydrocarbons, and disposing of it, which can represent a significant economic loss.
The production of water with desirable fluids may be addressed with conventional methods. For example, a treatment fluid including a resin may be injected downhole to reduce the production of water with desirable fluids. This method may include identifying a watered out section, cleaning the filter cake with an acid, and injecting a treatment fluid including a resin into the watered out zone so as to reduce the production of water. This conventional approach generally is undesirable because it increases the cost, time, and labor associated with the well. Additionally, if the water-bearing section is not identified accurately or sealed sufficiently, production of the desired fluid, as opposed to the undesired water, may be reduced, which is undesirable.
Another potential problem in the production of hydrocarbons involves unconsolidated portions of the subterranean formation, for example, unconsolidated sections of sand that may include water. Unconsolidated portions of a subterranean formation include those that contain loose grains of sand and those wherein the bonded grains of sand have insufficient bond strength to withstand forces generated by subterranean operations. Although unconsolidated sections of sand generally may be relatively easy to drill through while a positive differential pressure exists on the sand face, subsequent drilling operations may be problematic. For example, removal of the drill string from the bore hole may reduce the pressure across the boundary between an unconsolidated section of sand and the well bore such that the bore hole may collapse within the section of unconsolidated sand. Consequently, sections of unconsolidated sand that include a large amount of, or are saturated with, water can present prolonged difficulties during drilling and casing operations that may lead to the loss of a section of a hole.